Secondary school IGCSE-Solar-System.pptx

solar system

1. Solar System

2. Solar System Introduction Theory of formation The Sun A ‘Planet’ Planetary orbits Natural satellites (moons) Asteroids & Meteoroids Comets Click on the arrow to go to that section … or else hit enter/key-board arrow to proceed to the next slide 8 7 6 5 4 3 2 1

3. Solar System … the name for our “planetary system”, which is a set of gravitationally-bound non-stellar objects in orbit around a star, or star system.

4. Solar System The Sun and the eight planets - to relative size, but not orbital distance

5. Solar System The Solar system comprises:- Sun Planets, dwarf planets & minor planets Asteroids & meteoroids Comets Centaurs (a minor planet with an orbit roaming within the outer planetary region) Circumstellar discs - Kuiper belt, Oort cloud

6. Solar System To the edge of the Inner Solar System - the 4 ‘terrestrials’ (the rock planets) and the Asteroid belt

7. Solar System The Outer Solar System - the ‘gas giants’ (J & S), the ‘ice giants’ (U & N) and the ‘ centaurs ’ … and the Trans- Neptunian region (showing only the Kuiper belt ) Astronomical Units (‘au’) - the Earth-Sun distance 1 au = 149,597,870.7 km (by definition)

8. Solar System Pluto and Eris are ‘dwarf planets’

9. Solar System

10. Solar System Formation A nebula - a cloud of hydrogen, helium & other ionised elements collapses into a protosystem disc The proto-star starts fusion reactions when its mass generates enough gravitational pressure The proto-planets heat up from the kinetic energy captured from the accretion process, from gravitational pressure, and from the radioactive decay of any heavy elements that accretes into a proto-star at the centre, and surrounding it, proto-planets PAH … Polycyclic Aromatic Hydrocarbons

11. Solar System Support for this theory of formation:- - all planets and virtually all asteroids have prograde orbits around the sun - all planets have near circular orbits - all planets’ planes of orbit are within 5° of the sun’s equatorial plane - all planets except Venus and Uranus have prograde rotations on their own axese - all planets except Mercury and Venus have their own satellites - most satellites have prograde orbits around their ‘parents’ - direction of orbit is same as sun’s rotation … anti-clockwise The white moons are in prograde orbits The orange moon is in a retrograde orbit

12. Solar System Sun A sphere of hot plasma, mainly hydrogen and helium Surface temperature: 5500°C Core temperature: 15.7 mK Rotational period: 25.0 days (equator), 34.4 days (poles) Diameter: 109x Earth Mass: 330,000x Earth Surface gravity: 27.9x Earth - Ionised elements under high temperature/pressure conditions

13. Solar System Planet Orbits around the Sun Large enough to be ellipsoidal (but nearly spherical) under its own gravity but not to sustain nuclear fusion Cleared or captured (as a satellite) all other planetesimals in its orbital region ‘ Minor Planets ’ are all objects that orbit the Sun, excluding planets and comets > 550,000 catalogued objects as of 2021 ‘ Dwarf planets ’ do not meet condition 3 only e.g. Ceres (asteroid), Pluto, Haumea, Eris, Makemake (listed in order of discovery: 1801, 1930, 2004, 2005 & 2005)

14. Solar System Planetary data relative to Earth Mercury Venus Mars Jupiter Saturn Uranus Neptune Orbital radius: 0.382 0.718 1.52 5.20 9.55 19.2 30.1 Orbital period: 0.241 0.615 1.88 11.86 29.46 84.0 164.8 Diameter: 0.382 0.949 0.532 11.21 9.45 4.01 3.88 Mass: 0.06 0.82 0.11 318 95.2 14.6 17.2 Surface gravity: 0.38 0.90 0.38 2.53 1.07 0.89 1.14 Rotational period: 58.6 243 1.03 0.415 0.441 0.718 0.671 - see 3 slides forward for the links between Jupiter’s figures

15. Solar System

16. Solar System Orbital speed … in m·s -1 Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune 47,362 35,020 29,785 24,077 13,070 9,690 6,800 5,430 → Orbital speed decreases with increasing orbital radius - this is because the Sun’s pull gets weaker and leads to slower circular motion Earth’s rotational speed (equator): 465 m·s -1       E.g. Earth’s orbital radius is 149.598 m km, and it takes 365.256 days to complete one orbit … the orbital speed is:   https://www.bing.com/search?q=Solar%20System Scroll down the webpage to see the interactive solar system model

17. Solar System Orbits are due to gravitational force From the previous slide: … and substitution reveals: … or:         … or:   - for a given change in radius there is an change in period   Centripetal acceleration in circular motion Jupiter’s own surface gravity is stronger than Earth’s by 318 times due to its mass, but is weaker by ( 11.21 2 ) times due to its size – combined effect is 2.53 times Jupiter’s orbital period is longer than Earth’s by ( 5.2 1.5 ) times, at 11.86 times - see 3 slides back   ‘Host’/’parent’ mass mass of body being pulled Universal gravitational constant Radius of body separation   … and this is the only statement on this slide that you need to know !

18. Solar System Laws of Planetary Motion Planetary orbits are elliptical (but nearly circular), with the Sun at one focus of the ellipse - Strictly, the orbit of one body around another is elliptical around their combined centre of mass – the “barycentre” (the red + ) – at one focus … so long as one of the pair is significantly more massive, the barycentre is close to its own centre of mass and the smaller body is said to orbit around the larger. However, the larger body will have a noticeable wobble The orbital speed decreases as the orbital radius increases - we saw this decrease in orbital speed with the planets, the further away from the Sun they are - More formally expressed as: “a line joining the planet with the sun sweeps out equal areas in equal time intervals” - More easily understood as: the total energy ( k.e . + g.p.e .) of a body in orbit is conserved, and so there is a continuous transfer between high k.e.↔low g.p.e . in small orbital radii and low k.e.↔high g.p.e . in large orbital radii - this is particularly noticeable with the orbital speed of the comets, which speed up considerably as they near the Sun The squares of the orbital periods are directly proportional to the cubes of the semi-major axis of the orbit … more easily: for a given change in radius there is an change in period   - the solar system barycentre wander

19. Solar System Natural Satellites (‘moons’) - Orbit around a planet or minor planet - Most larger moons have prograde, uninclined, near-circular orbits - 19 are large enough to be ellipsoidal (but nearly spherical) - Some moons have ‘Trojan moons’ that share the same orbit at ±60° - Most larger moons are ‘tidally locked’ with their parents - Astronomical object in orbit around the sun that is not a planet or a comet - rotational period = orbital period … same face of satellite presented, e.g. Earth’s Moon - equatorial with their ‘parent’ Two bodies each revolving around their barycentre are ‘mutually tidally locked’, each presenting the same face to each other, never moving in the sky, and constitute a binary system, e.g. Pluto with its Charon https://www.youtube.com/watch?v=7hMfCCqSdFc Notice that the Earth does not rotate about the barycentre , but shifts as motion in a circle In contrast, both Pluto & Charon are rotating about the barycentre Pluto & Charon

20. Solar System - for information only Mars’ Phobos & Deimos are too small, at 22.2 km & 12.6 km diam., respec . (discovered in 1877) Ida’s Dactyl is shaped as a squashed rugby ball at 1.6 by 1.4 by 1.2 km (discovered in 1994)

21. Solar System Earth’s Moon - Orbital radius: 384,400km (~60 Earth radii ) - Orbital period: 27.32 days - Radius: 1,738km ( 0.273 x Earth) - Mass: 1.23% of Earth - Surface gravity: 1.62 m·s -2 ( × Earth) - Rotational period: 27.32 days - The Moon rotates about the Earth- Moon ‘barycentre’ (= combined centre of mass)   (at r = 4,671 km, or 1,700 km below the Earth’s surface) … but it’s elliptical orbit produces a 12% change in apparent size - less by a factor 0.0123 , and more by   … and its tidal forces are transferring the Earth’s angular momentum to increase this distance by 3.8 cm p.a. ⟵ Earth-Moon size & separation to scale ⟶

22. Solar System Asteroids & Meteoroids - from 1 m across to 975 m (Ceres) - below 1 m - are rocky/metallic objects - are rocky/metallic objects some are carbon-rich, some contain ices - exist in the asteroid belt, - exist throughout the solar system as ‘Trojans’ in Jupiter’s orbit and as some are comet debris (meteor shower) inner solar system minor planets (e.g. Ceres) - elliptical orbits, rarely crossing others - elliptical orbits, often crossing others called ‘meteors’ when visible, and ‘meteorites’ if they hit earth https://en.wikipedia.org/wiki/File:%D0%92%D0%B7%D1%80%D1%8B%D0%B2_%D0%BC%D0%B5%D1%82%D0%B5%D0%BE%D1%80%D0%B8%D1%82%D0%B0_%D0%BD%D0%B0%D0%B4_%D0%A7%D0%B5%D0%BB%D1%8F%D0%B1%D0%B8%D0%BD%D1%81%D0%BA%D0%BE%D0%BC_15_02_2013_avi-iCawTYPtehk.ogv The Chelyabinsk meteor of 15 Feb 2013 was estimated at ~20 m diameter, with a speed of ~19 km.s -1 and an energy of ~30x that of the Hiroshima bomb. It largely vaporised at a height of ~30 km, but the explosion produced numerous small meteorites

23. Solar System Comets Composed of dust, silicates, and frozen liquids and gases - CH 4 , NH 4 , H 2 O, HCN, CO, O 2 , CO 2 , C 2 H 5 OH Highly elliptical orbits, many extending far into the outer solar system, many highly inclined Orbital periods from years to millions of years Approaching the Sun, form a gaseous coma, a tail of small dust particles, & larger debris The coma is due to solar radiation causing sublimation of ices into an atmosphere of gases that the solar wind pushes directly away from the sun The tail particles are pushed off the comet’s orbital path by the solar wind and points in between the coma and the comet’s orbital path The debris continues in the comet’s orbital path Perhaps the best-known is ‘Halley’s Comet’, visible to the naked-eye, with a period of 75.3 yrs and an orbit extending to ~35 au, a little further beyond Neptune; next scheduled to “arrive” mid 2061.

24. Solar System Hale-Bopp (1997)

25. Solar System

26. Solar System